Co2 refrigeration system for ice-playing surface

ABSTRACT

A CO2 refrigeration system comprising a transfer circuit for heat exchange between a supracompression circuit of CO2 refrigerant, and an evaporation circuit of CO2 refrigerant. A transfer circuit absorbs heat from the evaporation circuit, and releases heat to the supracompression circuit. The supracompression circuit comprises a compression stage in which CO2 refrigerant is compressed, a cooling stage in which the CO2 refrigerant from the compression stage releases heat, and a pressure-regulating unit in a line between the cooling stage and the evaporation heat exchanger to maintain a pressure differential therebetween. The evaporation circuit receives CO2 refrigerant having released heat in the condensation heat exchanger. The evaporation circuit comprises a condensation reservoir in which CO2 refrigerant is accumulated in a liquid state, and an evaporation stage in which the CO2 refrigerant from the condensation reservoir absorbs heat to cool an ice-playing surface.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority on Canadian Patent Application No. 2,766,361 filed on Jan. 30, 2012, incorporated herewith by reference.

FIELD OF THE APPLICATION

The present application relates to refrigeration systems used to refrigerate ice-playing surfaces such as a skating rinks, curling sheets, etc, and more particularly to refrigeration systems using CO₂ refrigerant.

BACKGROUND OF THE ART

With the growing concern for global warming, the use of chlorofluorocarbons (CFCs) and hydrochlorofluoro-carbons (HCFCs) as refrigerant has been identified as having a negative impact on the environment. These chemicals have non-negligible ozone-depletion potential and/or global-warming potential.

As alternatives to CFCs and HCFCs, ammonia, hydro-carbons and CO₂ are used as refrigerants. Although ammonia and hydrocarbons have negligible ozone-depletion potential and global-warming potential as does CO₂, these refrigerants are highly flammable and therefore represent a risk to local safety. On the other hand, CO₂ is environmentally benign and locally safe.

SUMMARY OF THE APPLICATION

It is therefore an aim of the present disclosure to provide a CO₂ refrigeration system for ice-playing surfaces that addresses issues associated with the prior art.

Therefore, in accordance with the present application, there is provided a CO₂ refrigeration system comprising a transfer circuit for heat exchange between a supracompression circuit of CO₂ refrigerant, and an evaporation circuit of CO₂ refrigerant; a transfer circuit in which a transfer refrigerant circulates between a condensation heat exchanger to absorb heat from the CO₂ refrigerant of the evaporation circuit, and an evaporation heat exchanger to release heat to the CO₂ refrigerant of the supracompression circuit; the supracompression circuit comprising a compression stage in which CO₂ refrigerant having absorbed heat in the evaporation heat exchanger is compressed to at least a supracompression state, a cooling stage in which the CO₂ refrigerant from the compression stage releases heat, and a pressure-regulating unit in a line extending from the cooling stage to the evaporation heat exchanger to maintain a pressure differential therebetween; the evaporation circuit receiving CO₂ refrigerant having released heat in the condensation heat exchanger, the evaporation circuit comprising a condensation reservoir in which CO₂ refrigerant is accumulated in a liquid state, and an evaporation stage in which the CO₂ refrigerant from the condensation reservoir absorbs heat to cool an ice-playing surface, to then return to one of the condensation reservoir and the condensation exchanger.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of a CO₂ refrigeration system for ice-playing surface in accordance with an embodiment of the present application, with CO₂ refrigerant in a circuit under the ice-playing surface; and

FIG. 2 is a block diagram of a CO₂ refrigeration system for ice-playing surface in accordance with an embodiment of the present application, with CO₂ refrigerant cooling brine of a circuit under the ice-playing surface.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to the drawings and more particularly to FIG. 1, there is illustrated a CO₂ refrigeration system 1 for ice-playing surface, while FIG. 2 illustrates a CO₂ refrigeration system 2 for ice-playing surface similar to that of FIG. 1, whereby like reference numerals will refer to like elements.

In FIG. 1, the CO₂ refrigeration system 1 has a CO₂ evaporation circuit 10. The CO₂ evaporation circuit 10 comprises a condensation reservoir 12 accumulating CO₂ refrigerant in a liquid and gaseous state. The CO₂ evaporation circuit 10 is in a heat-exchange relation with a condensation circuit that absorbs heat from the CO₂ refrigerant.

Line 14 directs CO₂ refrigerant from the condensation reservoir 12 to an evaporation stage, with a flow of CO₂ refrigerant induced by pump and/or an expansion valve(s) as generally indicated as 15. As is shown in FIG. 1, the CO₂ refrigerant is then fed to the ice-playing surface evaporation stage 17.

The ice-playing surface evaporation stage 17 of FIG. 1 consists of a circuit of pipes positioned under the ice-playing surface, in which the CO₂ refrigerant circulates to absorb heat from fluid being frozen to form the ice-playing surface, or to maintain the ice-playing surface frozen.

CO₂ refrigerant exiting the evaporation stage 17 is directed to the condensation reservoir 12, by way of line 18.

The CO₂ evaporation circuit 10 is in a heat-exchange relation with a transfer circuit 20. The transfer circuit 20 is for instance of the type in which a transfer refrigerant (e.g., alcohol-based such as glycol, water, brine or the like) cycles. A condensation heat exchanger 21 is in fluid communication with the condensation reservoir 12, so as to receive CO₂ refrigerant in a gaseous state, whereby the transfer refrigerant absorbs heat from the CO₂ refrigerant in the heat exchanger 21. According to an embodiment, the condensation heat exchanger 21 has a coil that is positioned inside the condensation reservoir 12.

The condensation heat exchanger 21 may also receive CO₂ refrigerant directly from line 14, or from line 18. The transfer circuit 20 is a closed circuit featuring lines 22 and 23 as well as pump 24 to cycle the transfer refrigerant between the heat exchanger 21 and an evaporation heat exchanger 31 of a supra-compression circuit 30. Accordingly, the transfer refrigerant absorbs heat from the CO₂ refrigerant circulating in the CO₂ evaporation circuit 10, and releases the heat to the CO₂ refrigerant circulating in the supra-compression circuit 30.

In the transfer circuit 20, the condensation refrigerant circulates between the heat exchanger 21 in which the transfer refrigerant absorbs heat, and the heat exchanger 31 in which the transfer refrigerant absorbs heat.

The supra-compression circuit 30 (i.e., transcritical circuit if operated at transcritical pressures) is provided to compress CO₂ refrigerant to a transcritical state, for heating purposes, or supra-compressed state.

The heat exchanger 31 vaporizes the CO₂ refrigerant fed to a supra-compression stage 32. The supra-compression stage 32 features one or more compressors (e.g., Bock™, Dorin™), that compress the CO₂ refrigerant to a supra-compressed or transcritical state.

Upon exiting the supra-compression stage 32, the CO₂ refrigerant must be cooled by a cooling stage, embodiments of which are defined herein.

In the supra-compressed or transcritical state, the CO₂ refrigerant is used to heat a secondary refrigerant via heat-reclaim exchanger 34, via line 33. In the heat-reclaim exchanger 34, the CO₂ refrigerant is in a heat-exchange relation with a secondary refrigerant circulating in the secondary refrigerant circuit 35. Alternatively, the heat-reclaim exchanger 34 may be part of a coil of a convection heating unit, etc. In an embodiment, the heat-reclaim exchanger 34, whether directly or via the secondary circuit, is used to heat the water used in the ice-playing surface complex (for meeting the hot water demand for showers, etc), for heating the surroundings of the ice-playing surface, or for melting zamboni residue in the ice dump, among other possibilities.

The secondary refrigerant is preferably an environmentally-sound refrigerant, such as water or glycol (although other refrigerants could be used as well), that is used as a heat-transfer fluid. Because of the supra-compressed or transcritical state of the CO₂ refrigerant, the secondary refrigerant circulating in the circuit 35 reaches a high temperature. Accordingly, due to the high temperature of the secondary refrigerant, lines of smaller diameter may be used for the secondary refrigerant circuit 35. It is pointed out that the secondary refrigerant circuit 35 may be the largest of the circuits of the refrigeration system 1 in terms of quantity of refrigerant. Therefore, the compression of the CO₂ refrigerant into a transcritical state by the transcritical circuit allows the lines of the secondary refrigerant circuit 35 to be reduced in terms of diameter.

A gas cooling stage 36 is provided in the transcritical circuit. The gas cooling stage 36 absorbs excess heat from the CO₂ refrigerant in the transcritical state, in view of directing the CO₂ refrigerant to the heat exchanger 31. Although it is illustrated in a parallel relation with the heat-reclaim exchanger 34, the gas cooling stage 36 may be in series therewith, or in any other suitable arrangement.

Moreover, a geothermal gas cooling stage 37 may be provided, to use the geothermal cool to absorb heat.

Although not shown, appropriate valves are provided so as to control the amount of CO₂ refrigerant directed to the gas cooling stage 36, in view of the heat demand from the heat-reclaim exchanger 34. Moreover, a bypass line may be provided to bypass the heat-reclaim exchanger 34, the gas cooling stage 36 and the geothermal gas cooling 37.

A CO₂ pressure-regulating valve 39 is provided to maintain appropriate pressures at the stages 34 and 36, and in the heat exchanger 31. The CO₂ transcritical pressure-regulating valve 39 is for instance a Danfoss™ valve. Any other suitable pressure-control device may be used as an alternative to the valve 39, such as any type of valve or loop.

It is considered to operate the supra-compression circuit (i.e., supra compression 32) with higher operating pressure. CO₂ refrigerant has a suitable efficiency at a higher pressure. More specifically, more heat can be extracted when the pressure is higher.

Referring to FIG. 2, the CO₂ refrigeration system is similar to the CO₂ refrigeration system 1, but comprises an evaporation exchanger 16, by which the CO₂ refrigerant of the evaporation circuit 10 absorbs heat from a closed circuit of pipes of the ice-playing surface refrigeration stage 17. An alternative refrigerant circulates in the closed circuit of pipes of the ice-playing surface refrigeration stage 17, such as brine, glycol, or the like.

Although not fully illustrated, numerous valves are provided to control the operation of the CO₂ refrigeration system 1 as described above. Moreover, a controller ensures that the various stages of the refrigeration system 1 operate as described, for instance by having a plurality of sensors places throughout the refrigeration system 1. Numerous other components may be added to the refrigeration systems 1 and 2 (e.g., valves, tanks, pumps, compressors, pressure-relief systems, etc.), to support the configurations illustrated in FIGS. 1 and 2.

It is within the ambit of the present invention to cover any obvious modifications of the embodiments described herein, provided such modifications fall within the scope of the appended claims. 

1.-9. (canceled)
 10. A refrigeration system comprising: a compression stage in which refrigerant is compressed to a higher pressure state; a condensation stage in which the refrigerant in the higher pressure state releases heat; a pressure-regulating downstream of the condensation stage to lower a pressure of the refrigerant having released heat; and an evaporation stage in which the refrigerant absorbs heat to cool a fluid; wherein the condensation stage comprises geothermal gas cooling.
 11. The refrigeration system according to claim 10, wherein the evaporation stage comprises a heat exchanger in which the refrigerant absorbs heat from another refrigerant.
 12. The refrigeration system according to claim 10, wherein the condensation stage comprises a heat reclaim exchanger by which heat is reclaimed by another refrigerant for heating purposes.
 13. The refrigeration system according to claim 10, wherein the pressure regulating unit is at least one valve.
 14. The refrigeration system according to claim 13, wherein the valve is an expansion valve. 